The aim of this study was to identify whey-derived peptides with
angiotensin I-converting enzyme (ACE) inhibitory activity. The bovine whey
proteins α-lactalbumin and β-lactoglobulin were hydrolysed with pepsin, trypsin,
chymotrypsin, pancreatin, elastase or carboxypeptidase alone and in combination.
The total hydrolysates were fractionated in a two step ultrafiltration process, first
with a 30 kDa membrane and then with a 1 kDa membrane. Inhibition of ACE was
analysed spectrophotometrically. The peptides were isolated by chromatography
and identified by mass and sequencing analysis. The most potent inhibitory peptides
were synthesized by the 9-fluorenylmethoxycarbonyl solid phase method. Inhibition
of ACE was observed after hydrolysis with trypsin alone, and with an enzyme
combination containing pepsin, trypsin and chymotrypsin. Whey protein digests
gave a 50 % inhibition (IC50) of ACE activity at concentration ranges within
345–1733 μg/ml. The IC50 values for the 1–30 kDa fractions ranged from 485 to
1134 μg/ml and for the <1 kDa fraction from 109 to 837 mg/ml. Several ACE-inhibitory peptides were isolated from the hydrolysates by reversed-phase chromatography,
and the potencies of the purified peptide fractions had IC50 values of
77–1062 μM. The ACE-inhibitory peptides identified were α-lactalbumin fractions
(50–52), (99–108) and (104–108) and β-lactoglobulin fractions (22–25), (32–40),
(81–83), (94–100), (106–111) and (142–146).
Production of ACE Inhibitory Peptides from Whey Proteins Modified by High Intensity Ultrasound Using Bromelain
